46 Herbert Eugene Walter 



naria maculata,Dendroccelumand Phagocatawere chiefly obtained 

 from a pond at Falmouth, Mass., where they are especially abun- 

 dant. Twice, through the kindness of Professor Parker, aquaria 

 were generously stocked with Dendroccelum, from a spring on 

 Mount Monadnock, N. H. Bdelloura was obtained from Wood's 

 Hole, Mass., during the summer from freshly caught horseshoe 

 crabs and, later in the year, from specimens kept in captivity. 



The setting-up of balanced aquaria in which planarians would 

 thrive did not prove to be a difficult matter. The following 

 method, based largely upon suggestions by Wilhelmi ('04), was 

 used. Jars were filled to the depth of two or three inches with 

 cinders, dirt and dead leaves, over which was spread an equally 

 deep layer of clean sand. Clear water was then poured into the 

 remaining space and the whole allowed to settle, after which a few 

 such plants as Anacharis or Myriophyllum, with whatever micro- 

 scopic life might adhere to them, were added, together with a hand- 

 ful of large pebbles to diversify the bottom. The jars were kept 

 covered from dust in a cool place and occasionally a crushed snail 

 was dropped into each one to supply the worms with food. 



Planarians require pure water. Whenever for any reason the 

 water in which they are kept becomes foul they will desert their 

 places of concealment and crawl up the sides of the jar, while 

 water that has been standing in lead or iron pipes quickly causes 

 them to disintegrate. Rainwater or water taken directly from 

 some natural source, gives better results than that which has been 

 conveyed through pipes. Naturally the least chemical disturbance 

 takes place when the worms are kept in water dipped up at the 

 time and place of their capture. 



Planarians will live without being fed for over three months 

 when isolated in jars containing nothing except pure water, but 

 meanwhile they decrease regularly in size. It seems to be impos- 

 sible to "starve" them in the sense in which higher animals may 

 be forced to die from lack of food leaving behind a dead body. 

 These worms instead simply consume their own substance almost 

 to the vanishing point. 



During a part of the summer of 1905 observations and experi- 

 ments were carried on at the laboratory of the U. S. Fisheries 



